Marathon bombing suspect may blame brother

BOSTON — Dzhokhar Tsarnaev’s lawyers may try to save him from the death penalty in the Boston Marathon bombing by arguing he fell under the murderous influence of his older brother, legal experts say.

The outlines of a possible defense came into focus this week when it was learned that Tsarnaev’s attorneys are trying to get access to investigative records implicating the now-dead brother in a grisly triple slaying committed in 2011.

In court papers Monday, federal prosecutors acknowledged publicly for the first time that a friend of Tamerlan Tsarnaev told investigators that Tamerlan participated in the unsolved killings of three men who were found in a Waltham apartment with their throats slit, marijuana sprinkled over their bodies.

The younger Tsarnaev’s lawyers argued in court papers that any evidence of Tamerlan’s involvement is “mitigating information” that is critical as they prepare Dzhokhar’s defense. They asked a judge to force prosecutors to turn over the records.

Dzhokhar Tsarnaev, 20, faces 30 federal charges, including using a weapon of mass destruction, in the twin bombings April 15 that killed three people and injured more than 260. Tamerlan Tsarnaev, 26, died in a gunbattle with police days later.

The government is still deciding whether to pursue the death penalty for the attack, which investigators say was retaliation for the U.S. wars in Muslim lands.

Richard Dieter, executive director of the Death Penalty Information Center, said the defense may be trying to show that the older brother was the guiding force.

“If I was a defense attorney and was seeking perhaps to draw attention to the influence the older brother had in planning the bombing, I would use his involvement in other crimes to show that he was likely the main perpetrator in the Boston bombing,” Dieter said.

“I would take the position that my client, the younger brother, was strongly influenced by his older brother, and even if he is culpable, the death penalty is too extreme in this case.”